1. Field of the Invention
The present invention relates to a suspension coil spring that is used for a strut type suspension for a vehicle, and a strut type suspension that includes the suspension coil spring.
2. Description of the Related Art
Recently, a strut type suspension that is widely spread as a suspension for a vehicle is configured such that a shock absorber is used as a positioning stay (strut) with respect to a wheel. The shock absorber, as a strut, includes a cylinder; a rod that is slidably supported by a cylinder; and a suspension coil spring that is provided at an outer circumferential side of the rod.
In this strut type suspension, an upper end of a rod is connected to a vehicle body through a strut mount or the like, and at the same time, a lower end of a cylinder is rigidly joined to a knuckle that supports a wheel, so that the wheel can be rotated. The knuckle is pivotably joined to the vehicle body through a lower arm.
Further, the suspension coil spring is disposed between an upper side pedestal that is fixed to the side of the vehicle body and a lower side pedestal that is fixed to the outer circumferential side of the cylinder, so that the suspension coil spring is in a compressed state. The suspension coil spring is supported at the outer circumferential side of the rod.
The above-described strut type suspension is advantageous compared to those of other independent suspension types because the number of the parts can be small, the structure can be simple, and an installation space can be small.
However, in a strut type suspension, an axis of the strut is shifted relative to a load input axis (the axis that connects a tire grounding point and an upper mount point of the strut), so that bending moment can be generated in the strut. The bending moment can cause lateral force to be applied to the sliding portion of the shock absorber. Thus, the friction of the rod can be increased, and a smooth motion of the shock absorber can be prevented. Consequently, the bending moment can be a cause of degrading riding comfortableness of the vehicle.
As a method of reducing such bending moment, it has been proposed to deform the shape of the suspension coil spring, or to provide a reinforced stopper at a coil end. As a method of reducing by deforming the shape of the suspension coil spring, for example, Patent Document 1 proposes a configuration such that the strut is inserted into the suspension coil spring while decentering the suspension coil spring to the strut, and a pigtail coil end is provided at a lower portion of the suspension coil spring. Here, the pigtail coil end is decentered to and linked to the suspension coil spring. Further, Patent Document 2 proposes a configuration such that a spring center line of the suspension coil spring has an S-shape in an unloaded state.
Further, as a method of reducing by providing a reinforced stopper, for example, Patent Document 3 proposes a configuration such that a plurality of protrusions is provided at an coil end, and some protrusions of the plurality of the protrusions are selectively contact a spring pedestal depending on the weight of the load that is applied to the suspension coil spring. Furthermore, Patent Document 4 proposes a configuration such that one reinforced stopper is provided at an upper side pedestal of the suspension coil spring and one reinforced stopper is provided at a lower side pedestal of the suspension coil spring.
PATENT DOCUMENT 1: Japanese Examined Utility Model Publication No. S58-032970
PATENT DOCUMENT 2: Japanese Patent No. 2642163
PATENT DOCUMENT 3: Japanese Patent No. 4336203
PATENT DOCUMENT 4: European Patent Publication No. 728602